Signal system for controlling street traffic



B. W. DAVIS.

SIGNAL SYSTEM FOR CONTROLLING STREET TRAFFIC. APPLICATION FILED OCT-30.1914.

1,328,269. Patented Jan. '20, 1920.

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SIGNAL SYSTEM FOR CONTROLLING STREET TRAFFIC.

APPLICATION FILED OCT- 30, I914.

1 Patented Jan. 20,1920.

3 SHEETS-SHEET 2.

m-EWWM MMT'PWIEJ fl B. W. DAVIS.

SIGNAL SYSTEM FOR CONTROLLING STREET TRAFFIC.

APPLICATION FILED OCT-30.19M-

1,328,269, Patented Jan. 20, 1920.

3 SHEETS-SHEET 3- BENJAMIN W. DAVIS, OF CHICAGO, ILLINOIS.

SIGNAL SYSTEM FOR CONTROLLING STREET TRAFFIC.

Application filed October so, 1914. Serial No. 869,446.

To all whomz't may concern:

Be .it known that I, BENJAMIN W. DAVIS, acitizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Signal Systems for Controlling Street Traffic, of which the following is a specification,

This invention relates to signal systems and has for its principal object to'provide a signal system for use in controlling trailic at street intersections.

It is now common practice to place at the intersectlons of busy streets in cities traffic policemen who control the passage'of traffic by means of whistles or by signaling with their arms. This method of traffic control usually requires more than one traffic officer at each intersection, especially where the streets are very busy, and is open to the further objection that thesignals are often confusing and not discernible. \Vhistles are often indistinct, or the sounds of whistles at neighboring street intersections are intermingled and confused, and their use1necessitates that persons using the street be con stantly on the alert to determine the number of blasts sounded.

The present invention aims to overcome these and many other disadvantages of :present methods of trafiic control.- by providing a system comprising distinctive signals easily discernible to the eye for indicating which street is open for traflio' and which street or streets are closed to. traffic at the intersection.

Another object is to provide a signal system actuated by an electric circuit, so arranged that the indication of the clear.

signal for one street may be given simultaneonsly with the block or danger signal for the other intersecting street or streets.

A further object is to provide a signal system which may be readily and'conveniently operated by a signal traffic officer at each 7 street intersection.

Still another object is to provide means for permitting operation of the signal system by the traffic officer in a wide range of positions adjacent the street intersection.

These and other objects will be more specifically set forth in the following specifica tion taken in connection with the accompa-nying drawings, in which;

Figure 1 shows diagrammatically the circuit connections andgen'eral arrangement of Specification of Letters Patent.

Patented Jan. 20, 1920.

signal apparatus at the point of intersection of two streets;

Fig. 2 shows a side elevation of the signal apparatus for the intersection of two streets showlng a portion of one of the supporting posts broken away;

Fig. 3 is an enlarged detail of the righthand supporting post shown in Fig. 2 with a portionof the wall thereof broken away to disclose the arrangement of the cable within;

Fig. shows a reduced plan view of the signal system shown in Fig. 2;

Fig. 5 shows a plan view of thesig'nal sys tem for use at the point of intersection of three streets;

Fig. 6 is anenlarged perspective view of the signal member for the system shown in Fig. 5;

Fig. 7 is a diagrammatic view showing the circuit connections and operating switch for the signal system shown in Figs. 5 and 6;

Fig. 8 shows an enlarged longitudinal sec- 1 tion of the drum which supports the cable; Fig. 9 shows an enlarged end View of the drum shown in Fig. 8;

Fig. 10 shows a diagrammatic View of the arrangement and connections of signals for giving corresponding signals simultaneously at several different street crossings;

Fig. 11 shows a contact maker for use in automatically controlling a signal system;

Fig. 12 shows a modification of the device illustrated in Fig. 11;

Fig. 13 showsTa plan view of a signal arrangement for the intersection of a street by a railway line; and

Fig. 14 is a plan view of astreet intersection showin ,a modified arrangement of the signal mem ers.

Like numerals and letters of reference refer to like parts and elements in the several figures of the drawings.

Referring to Fig. 2 the signal member 10 is shown as comprising four radiating signal elements or vanes 11, the opposite pairs of which lie ineplanes transversely of the streets 12 and -13, the boundaries of which are indicated in dotted lines Fig. 1 and by full lines in Fig. 4. The signal member. 10 may be supported by any suitable means and is preferably rigidlysecured by means of brackets or clamps 14. or other suitable means, to two parallel wires or cables 15 and 16 which are secured at their ends by any suitable means to the supporting posts I! and 18 which are locatedvin this construetion at diagonally opposite street corners as shown in Fig. 4. When desired, the signal *member may be mounted on a single post located at the center of the street crossing area or in any other suitable place as shown in Fig. 14, or, for instance, as shown at 24 in Fig. 14, in which case the complete signa member for the two streets comprises two separate integral parts.

Each radiating signal element 11 has a portion of each opposite vertical face 19 formed of a sheet of stained glass or other suitable material of a distinctive color, so that when the interior: of the signal element is illuminated a light of a distinctive color will be projected from each signal element in Opposite directions along the street which passes normally to the plane thereof. The vertical faces 19 of opposite signal elements for the same street have their walls formed of plates of different colors so that one sig-.

nal element'may be actuated to indicate that the street is clear for traffic, while the other may be used to indicate that the street is closed to traflic. For instance, the signal element-s may have walls red and green in color, as indicated by the letters G, G and R', R The interior of each signal element 1s illuminated by electric lights preferably two or more in number, as shown by dotted lines at 20. If preferred the faces 19 of the signal elements may be colorless and colored lightsmay be used within or with colored lights the faces may be omitted. The ends 19 of the signal elements and the central partitions 19 shown in Fig. 6, are of some opaque material to prevent interference between the signals of different color and to prevent the projection thereof in improper directions.

As shown ,in Fig. 1 the green signal element for one street has its lights connected in parallel with those on the red signal element for the other intersecting street. One side of each of these parallel circuits is connected to a common feed wire 21 and the other side of each parallel circuit is connected to one of the wires 22 and 23. The wires 21, 22 and 23 are preferably carried in a conduit 24 from the signal member 10 to a cut-out box 25 near the upper extremity of the supporting pole .18. From the cut-out box 25 the common feed wire 21 and the return circuit feed wire 26 extend downwardly in a circuit along the pole through aswitch box 27 and cut-out switch 28 to the supply circuit beneath the street level. From the cut-out box 25 the return circuit feed wire 26 and the two wires 22 and 23 are formed in a flexible cable 29. At the end of the flexible cable 29 the wires 22, 23 and 26 are connected to a switch member 30 which may be actuated by the traflic officer to control the operation of the signals. Within the switch member 30 the .common return means of the pivoted lever 37 and whichterminate in the rounded heads 38 of conducting material of suitable form to pass between the spring blades 3133 and 31-34= and to be engaged by the inwardly projecting portions 32 of said blades. It will thus be seen that when one push plug 35 is pushed inwardly with respect to the switch casing a connection will be formed between the conductors 22 and 26, for instance, thus illuminating the signal elements R and G \Vhen the other push plug is pushed inwardly to engage the contact blades 131-3 1, the first mentioned push plug will automatically pass out of engagement with its corresponding cont-act blades 31- 33, thereb extinguishing the signal elements R and (x and the signal elements R and G will be illuminated. hen the signal elements R and G are illuminated persons on the street will know that the trafiic is free to pass. along the street 12 while passage is forbidden along the street 13, and when the signal elements just mentioned are darkened, R and G will be lighted and persons on the street will know that the traflic is then free to pass along the street 13 at the intersec-tion while its passage is forbidden along the street 12.

In order to permit the traflic oflicer to assume a wide range of positions adjacent the street intersection the flexible cable 29 is passed over a pulley 39 suitably mounted on the supporting post 18 adjacent the upper extremity thereof. On the side of the pulley 39 opposite the switch member 30 the cable 29 then extends downwardly in the form of a loop and has mounted thereon the traveling weight 40 carried by a pulley or drum 41 which coacts with the cable. When the traffic oflicer desires to assume a position outwardly from the pole 18, a downward pull on the outer end of the cable 29 will elevate the weight 40 and lengthen the cable at the outer side of the pulley 39. The drum or pulley 39-is preferably rotatably mounted on a shaft 39 which has secured thereto a modified ratchet wheel 39 having a notch adapted to coact with the pawl 39 secured to the end of the drum. The drum is'preferably recessed to receive the pawl and ratchet and a plate 41 fits over the end of the drum to close the recessed operation of a window curtain and maintained in any desired position. The weight 40 is preferably suspended within the supporting post 18 which is of a hollow construction, as shown in Figs. 2 and 3. A suitable block 42 is rigidly secured to the cable 29 at the outer side of the pulley 39 to limit the, downward movement of the weight 40 and this block 42 is preferably so located as to bring the switch member 30 opposite the switch box 27- when said block 42 is in engagement with the pulley 39 so that when it is desired to discontinue the operation of the signal system, the cable 29 may be passed into the slot 43 in the lower 'face of the box 27 after the switch 28 has been thrown into open position. The door 27 of the switch box 27 may then be locked and access to the signal system prevented while the trafiic oflicer is off duty.

In Fig. 13 I haveshown a street 12 intersected by a railway line 13 in which case the signal member comprises green and red signal elements. actuated by an electric circuit comprising cables 24 and 24 which lead to contact makers 25*, of a well known form, adapted to be actuated by the wheel flanges or other parts of passing cars. The circuit connections may be arranged to actuate the green and red signal elements in any desired manner, as will be apparent to those skilled in the art.

In Figs. 5, 6 and 7, I have illustrated the circuit connections and arrangement of ele- 35 ments of asignal system to be used at the intersection of three streets. In this case the signal member is preferably formed of threeintegral parts 45, 46 and 47, each comprising the red and green signal elements for one street. If desired, the signal member may be .constructed according to this plan for use at the intersection of two streets, especially where they do not intersect at right angles. These separate members 45, 46 and 47 may be secured together by any suitable means and sup ported preferably between wires or cables 48 and 49 as in the previous case. The green and red signal elements are indicated in 50 this case by the characters g, g, g and 'r', r 1- and are connected as shownin Fig. 7, the common feed wire 21 being connected to one terminal of the lamp circuit for each signal element. The other terminals of the lamps for the green signal elements 9, g and. g are connected by means of the conductors 50,- 51 and 52 to'contact blades 53, 54 and 55, within the switch member 30. .The lam circuits of the red signal elements 1', 7' an 1' are connected by means of conductors 56, 57 and 58 to the respective contact blades 59, 60 and 61. The contact blades just mentioned are similar in form to those previously described and those for 65 the red signal elements terminate in alineresponding street. The plugs 63 are pro-' which have heads 64 of suitable form to be tightly gripped between the projections of the contact blades 62 and the correspond: ing projecting extremities of the contact blades 53, 54, 55 and 59, 60 and 61'. -When the push buttons are in their normal positi'on as shown in Fig. 7 they make contact between the blades. 62 and each of the blades 59, 60 and 61, thus closing the circuits through the red signal elements 1", 1' and f, thereby indicating that each of the three intersecting streets are closed; to. the .passage of traflic. When one of .the push plugs 63 is pushed inwardly its head 64 makes con-" tact between a blade 62 and one of-the blades 53, 54 or 55, thereby closingthe circuit for one of the green signal elements to indicate that the traflic is free to pass along the cor- '95 vided with insulating rings 6'4 adjacent the heads 64 so that when a plug is pushed in.- wardly to light a green signal, the circuit for the corresponding red signal will be broken.

At the same time that one of the push plugs 63 is pushed inwardly to close the cir.- cuit for agreen signal-element, the other two .push plugs should remain in the nor-' mal position shown in Fig. 7 so as to main tain a closed circuit for the red signal ele ment of the two other intersecting streets, and to accomplish this purpose automati cally, a system of levers are associatedwith the'push plugs so that when one of them is pushed inwardly the other two will always be in the outer normal position. This mech' anism comprises three levers 65, one which is pivoted toeach of plugs 63 and two other levers 66 which are piv- I15 oted on the switchcasing. Each of the levers 66 is arranged to coact at each end thereof with the adjacent extremity-of one of the levers 65,''and each of the outer levers 65 has its outer extremity arrangedjto 120 engage a notch 67 in the switch casing. At some oint, preferably within the notches 67, su cient backlash is leftinthe systemv of levers, as represented by the clearances 68, to permit one of the push plugs to be 128 moved inwardly the proper amount -to illuminate a green signal element, while the other two are in their outer normal position. If thereafter one of the other push plugs be pushed inwardly thelast mentioned 18.

push plug'will, through the operation of the levers, be caused to move outwardly to its normal position so that when the green lights are burning for one street of the in- 5 tersection, the red lights will be burning for the other two streets of the intersection, and this adjustment is made merely by pushing inwardly one of the push plugs.

In many instances, especially on very busy streets, it may be desirable, during certain hours of the day, to simultaneously operate the signals at difl'erent street crossings in such manner that the traflic will move in the same dlrection simultaneously in successive blocks of the same street, or on parallel streets. When the signals at different street intersections are actuated independently by individual traflic oilicers, it will be seen that the clear signals,-indicating that the traific is free to pass along a given street,

will be given at different times by the oflicers at the dlfi'erent successive intersections along the same street,.so that vehicles will be frequently interrupted and will be -unable to pass continuously for any great space of time in one direction. It is, therefore, desirable to arrange the signal system for con trolling the traffic in suchmanner that the clear signals, or the danger signals, will be given simultaneously at successive street intersections for the same street, and the provision'of such a system constitutes a very important feature of the present invention.

and 73, the boundaries of these streets be- 40 -'ing indicated by dotted lines. The signal members and the electriccircuit for actuating the same are shown diagrammatically in their proper relation to the intersections of the above-named 's't'reets, the red and green signal elements of each signal member being designated by the letters It and G, respectively.

It will be seen that the green signal elements for the streets 70 and 71 at each intersection are connected in parallel with the red signal elements for the streets 72 and 73 at the corresponding intersections, while the green signal elements for the streets 72 and 73 are connected in parallel with the red .55fsignal elements for the streets 70 and 71.

Each of these parallel circuits has one side thereof connected to a common feed wire designated by the numeral 7 4; the other terminals of the parallel circuits of the class first mentioned. are each connected to a common conductor 75; and the other terminal of each parallel circuit of the class last mentioned is connected to a common conductor 76; the conductors 74, 75 and 76 correspond ated by the operator for simultaneously controlling the signals at different street intersections.

It will be evident from a study of the connections above described that when the green signal element is actuated at a given street intersection to indicate that the traffic is free to pass along one street of the intersection, the proper green signal elements at the other intersections will be simultaneously actuated to indicate that the trailic is free to pass at those intersections along the given street and, if so arranged, along other parallel streets. By this method of traflic control drivers of vehicles may observe signals two or more blocks in advance of their position and may suitably regulate their speedso as to passcontinuously for a considerable distance without interruption. A further advantage of this method lies in the possibility of so actuating the signals as to permit the traific to pass for relatively long periods of time along-streets having the greatest volume of traflic while allowing only relatively short periods for the traflic to pass on the intersecting streets having a lesser volume of trafiic. v Where the traflic on the streets is -fairly uniform in quantity, the signal system may be automatically actuated by a contactmaker of a well-known form which may be driven by a motor, or otherwise, to change the circuit connections at fixed intervals. In Fig. 11 I. have shown such a contactmaker, comprising a semi-circular plate 71,

which is mounted on a shaft.7 9, to be continuously driven by a motor or other means; the common return conductor 77 vmay be connected to this disk, and the two conductors 75 and 76 connected to brushes 80 and 81, one or the other of which is always in contact with the plate 71 so as to complete the circuit for one set of signals.-

With' a half revolution of the shaft 79 the circuit connections and setting of the signals will be changed, thus giving equal periods of time for the traflic to pass the intersection on each of the intersecting streets.

Where the traflic along some streets is greater in volume than that along other intersecting streets, it may be desirable to use a contact-maker of the form shown in Fig. 12, in which the brushes 80 and 81 are adapted to contact with arcuate cam surfaces 82 and 83 of difi'erent lengths and at different timesfso that the circuit connection for one set of signals will be maintained during a longer interval than the circuit connections for the other set of signals,

thus permitting trafl'ic to pass a greater length of time on the streets having the greatest volume of traific.

- By means of the system of control just def scribed, it may be possible to avoid the nepointed out, is that the indication of the.- signalscan be observed by pedestrians, as

"well as by drivers of vehicles, some dis-.

tance before the street crossing is reached,-

so tha'tsuch driver or pedestrian mayknow before reaching the crossing whether or not 7 traflib is'free to pass in the direction he wishes to go without the necessity oflooking or listening for signals .which cannot readily beldistinguished. This is of a special advantage to automobilists who may observe the change or time duration of a given set of signals before reachinga street intersection and thus be'enabled to form a definite plan of'action before reaching'such intersection and thus avoid, in many instances,

the necessity of completely. stopping their automobiles; for instance, by increasing speed the driver may cross the intersecting street .before'the signal changes, or by decreasing speed, avo d reaching the crossing 40 until the same is opened to him.

While Ihegze described a specific embodiinent of mylinyention for the purpose of illustratingfth" nature and advantages thereof, it willbe understood that it may be modified-in formiand arrangement without departing from the' s00 e of'the invention as define by the appen ed claims,

What Iiclaim v is 1. In,a'. 1gn' al system forpontrollinglstreet 5 0 trafiic, a;, s1gnal member comprising distinctive signal elements, an electric circuit for illumlnating'said signal elements, said circuit comp an extensiblet cable, and

a switchmember carried by said bable.

y -2-. In a signal system for controlling street traflic, signal members located adjacent each of a pluralityof street intersections, each signal member comprising a danger Sig: nal element and a clear signal element for eachstreet of the adjacent intersection, and

means to actuate the clear signal ele ments for parallel streets at difi'erent intersections, and the danger signal elements forthe streets which intersect said parallelstreets at those intersections simultaneously, said means comprising an automatic contact-maker. 1

3. In a signal system for-controlling street traflic, a sign-a1 member comprising distinctive signal elements, a supporting structure for said signal member, an electrlc circuitfor actuating saidsignal member, a

switch for the electric circuit, said circuit.

including a flexible cable by which said switchis carried, and means for varying the effective length of said flexible cable.

n a signal system ofthe class described,a signal member. comprising a plu-.

rality of signal elements, a supporting struc ture comprising a hollow. ost, an electric circuit for actuating said jsignal elements,

said circuit comprising a. flexible cable having apart thereof disposed'twithin said hollow post, means carried by"said post for regulating-the length of cable on the outer side of. said post, and means carried by said cable for controlling said electric circuit.

5; In a signal system for controlling traf- -fic at intersecting ways,'in combination, signal members positioned at the intersection of said ways, each ofsaid membersjh'aving a danger indicating element and a clear Indicating element for each of the intersecting ways, means for actuating said member, sald means being-arranged to project aclear signal. in both directions along one of said Ways and a danger signaliin both directions along the intersect-.

ing ways, and means for controlling saidactuating meansfrom a plurality of points, said latter means including an extensible 7 cable.

In testimony whereofyI have subscribed my name.

Witnesses: 4

GLEN E. SMITH,

HENBY A .PARKS.. v j

BENJAMIN w. DAV S. 1' 

